Sinclair Institute Products Erection Ring Set contains four stretchy rings for firmer erections. Four stretchy erection rings in a variety of sizes and strengths. Each of these rings strengthen and maintains weak erections and restores ability for intercourse. Each ring is designed with easy-to-grip, easy-to-use handles, allowing quick on/off in seconds. These erections rings can be used with the Sinclair Institute Select Endow Vacuum Pump System or similar penis pumps. When worn around the base of the penis and testicles, many users find that cock rings increase sexual pleasure. Phthalate-free, latex-free, PVC-free Thermoplastic Rubber TPR. Sinclair Institute Select Erection Rings Set.